Systems and methods for ocular measurements

ABSTRACT

A system for measuring the size of a capsular bag of an eye of a subject includes a size indicator and a sizing gauge. The size indicator is configured for insertion into a capsular bag and includes a peripheral portion and a pair of arms. The peripheral portion is configured to engage the capsular bag. Each of the arms has a proximal end and a distal end, the arms being joined to one another at the proximal ends. The peripheral portion is joined to the distal ends of the arms. The arms form an angle that depends on a size of the capsular bag into which the size indicator is placed. The sizing gauge has a body having a front surface, along with first and second features disposed along or behind the front surface. The features are configured to correspond to an angle that is within a predetermined range of angles of the arms of the size indicator when the size indicator is placed within a capsular bag.

RELATED APPLICATION

The present application is a continuation-in-part of, and claimspriority to, U.S. patent application Ser. No. 11/739,392, filed Apr. 24,2007, and also claims priority under 35 U.S.C §119(e) to provisionalapplication No. 61/040,638, filed on Mar. 28, 2008, the entire contentsof each of which applications are hereby incorporated by reference intheir entirety for all purposes as if fully set forth herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to devices, systems, and methodsfor making and using ocular measurements, more particular for making andusing ocular measurements of a cavity size within an eye such as thecapsular bag of a human eye.

2. Description of the Related Art

A great deal of effort has been devoted to developing an accommodatingintraocular lens, which can adjust its power over a particular range toclearly view both near and far objects. The accommodating intraocularlens is generally inserted into a capsular bag, a transparent structureof an eye that houses the natural lens and generally remains in the eyeafter the natural lens has been surgically removed.

The accommodating intraocular lens changes its power and/or axiallocation in response to a squeezing and/or expanding force applied tothe lens by the capsular bag via the ciliary muscle.

It is generally important to know the size (or more precisely, the innerdiameter or circumference) of the capsular bag for each patient's eyeprior to insertion of an intraocular lens. The capsular bag size mayvary patient-to-patient or eye-to-eye of the same patient, and if thebag is larger or smaller than expected, the lens may end up slightlyexpanded or squeezed upon implantation. This, in turn, may result in ashift in the nominal base power and/or a reduction in the accommodationrange.

Although the capsular bag diameter is a desirable and useful quantity,it is also quite difficult to measure accurately. There have beenvarious attempts to measure the capsular bag size with ultrasound. Whileultrasound may be useful for determining the central thickness of thenatural crystalline lens, it is not generally versatile enough to imagethe entire lens, and cannot reliably read out to the perimeter of thelens.

There have also been attempts to measure the capsular bag by inserting acapsular tension ring (CTR) into the eye. See, for instance, K. STRENN,R. MENAPACE, and C. VASS, “Capsular bag shrinkage after implantation ofan open-loop silicone lens and a poly(methyl methacrylate) capsuletension ring,” J Cataract Refract Surg, 1997, pp. 1543-1547, Vol. 23,which is hereby incorporated by reference in its entirety. In thisreference, a CTR indicates the capsular diameter, based on linearmeasurement of a peripheral gap. After the measurement, the CTR isgenerally not removed from the eye and remains resident in the eye,which may be undesirable.

There have been attempts to correlate capsular bag size with other eyeproperties that can be measured more easily. See, for instance, C. VASS,R. MENAPACE, K. SCHMETTERER, O. FINDL, G. RAINER AND I. STEINECK,“Prediction of pseudophakic capsular bag diameter based on biometricvariables,” J Cataract Refract Surg, October 1999, pp. 1376-1381, Vol.25, which is hereby incorporated by reference in its entirety. In thisreference, measurements of capsular bag diameter were taken on a sampleof patients, using the CTR noted above. In addition, measurements ofcorneal power and axial length were taken on the same patients, usingknown methods. A regression analysis of the measurements produced astatistically significant correlation between capsular bag diameter andcorneal power and axial length, but not with a sufficient accuracy forpredicting the required size of an accommodating intraocular lens.

There have also been attempts to convert the capsular bag circumferencedimension to a linear dimension, then to measure the linear dimensionwith a camera or visually. See, for instance, M. TEHRANI, H. B. DICK, F.KRUMMENAUER, G. PFIRRMANN, T. BOYLE and B. STOFFELNS, “Capsule measuringring to predict capsular bag diameter and follow its course afterfoldable intraocular lens implantation,” J Cataract Refract Surg,November 2003, pp. 2127-2134, Vol. 29, which is hereby incorporated byreference in its entirety. In this reference, a Koch capsule measuringring is inserted into the eye. The ring is an incomplete circle, withappendices on each end, so that when the ring is inserted into thecapsular bag, the separation between the appendices is related to thecapsular bag circumference. The ring is left in the eye after themeasurement is taken, which may be undesirable.

In addition, for the above reference, the measurement of the appendixseparation may be disadvantageous for two reasons. First, themeasurement is taken at the peripheral edge of the eye, which is adifficult region for eye measurements. For instance, the region to bemeasured might be outside the area of the pupil, and might require theuse of a slit lamp, or unusual and undesirable handling of the pupil.Second, it is generally difficult to measure a linear dimension in theeye. Often, such a measurement is taken through the cornea, which canmagnify the linear dimension, especially at the periphery of the eye.Because corneal powers may vary from patient-to-patient and eye-to-eye,there may be uncertainty in any linear measurements taken through thecornea. In addition, because most eye surgery is performed through amicroscope, the measurement may have to be taken through the microscope,which may have a zoom feature or a variable focal length that mayfurther complicate a linear dimension measurement.

Accordingly, there exists a need for an apparatus and method formeasuring the size of the capsular bag of an eye that is relativelysimple and accurate, and does not rely on a linear measurement at theperiphery of the eye.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow chart of a method of replacing a lens in the capsularbag of an eye.

FIG. 2 is a front-view plan drawing of an angle indicator according toan embodiment of the present invention.

FIG. 3 is a schematic drawing of the angle indicator of FIG. 2 at threeexemplary capsular bag sizes.

FIG. 4 is a schematic drawing of an approximate geometry of the angleindicator of FIGS. 2 and 3.

FIG. 5 is a plot of capsular bag diameter versus measured angle A, for avariety of straight segment lengths, for the approximate geometry ofFIG. 4.

FIG. 6 is a close-up of the q=0.6 plot of FIG. 5.

FIG. 7 is an isometric drawing of a protractor according to anembodiment of the present invention.

FIG. 8 a set of views of the protractor of FIG. 7.

FIG. 9 is a plan view of a sizing gauge according to an embodiment ofthe present invention.

FIG. 10 is a plan view of a sizing gauge according to an embodiment ofthe present invention that includes a handle or grip.

FIG. 11 is a plan view of a system according to an embodiment of thepresent invention where a sizing gauge is disposed over an angleindicator placed within the capsular bag of a subject eye.

FIG. 12 is a plan view of another embodiment of a sizing gaugeincorporating a plurality of linear marks or line segments.

FIG. 13 is a plan view of a system according to an embodiment of thepresent invention where the sizing gauge of FIG. 12 is disposed over anangle indicator placed within the capsular bag of a subject eye.

FIG. 14 is a perspective view of another embodiment of a sizing gaugethat comprises two notches or wedge-shaped portions.

FIG. 15 is a perspective view of a kit or set of sizing gauges like thesizing gauge shown in FIG. 14.

FIG. 16 is a front view of a kit or set of sizing gauges like the sizinggauge shown in FIG. 14 that are joined together to facilitate choosingdifferent gauges during use.

DETAILED DESCRIPTION OF THE DRAWINGS

Implantation of an intraocular lens in an eye may require the accuratemeasurement of the size, position, or other property of the capsular bagof the eye. Embodiments of the present invention are generally directeddevices, systems, and methods for determining the size, extent,location, or physical property of a capsular bag or other cavities of asubject eye. While such devices, systems, and methods may be used inconjunction with any intraocular lens or similar device to be placedwithin a capsular bag, embodiments of the present invention may beparticularly useful when used with accommodating intraocular lenses,where function of the intraocular lens may be particularly sensitive tofit of the lens inside the capsular bag.

In some embodiments, the natural crystalline lens is surgically removedand a size indicator is subsequently inserted into the capsular bag formeasuring a size or other property of the capsular bag. As used herein,the term “size” means the extent of an object and includes at least thediameter, circumference, cross-sectional area, and volume of an object(e.g., of the capsular bag of an eye). As used herein the term “sizeindicator” means a physical device that changes size or shape whenplaced inside the capsular bag of an eye, or some other part of an eye,and is configured to allow an estimate or measurement of a size of thesize indicator itself and/or a size, shape, or physical property of thecapsular bag or cavity into which the device is placed, the estimate ormeasurement being based on a visible size or shape of one or moreelements of the size indicator. In some cases, the size indicator may beused for determining the position of the capsular bag, for example,relative to the pupil of the eye. When a size of a capsular bag ismeasured or estimated, the size may be an actual size of a capsular bagat the time of the measurement or a size of the capsular upon or afterimplantation of an intraocular lens or similar ophthalmic device.

In some embodiments, the size indicator is visually inspected by a userto make an estimate of size of the size indicator and/or the capsularbag or other part of the eye. In such embodiments, a geometric featureof the size indicator may be compared to a feature of a measurementdevice or to a template showing different configurations of thegeometric feature being inspected. In other embodiments, the sizeindicator is part of a measurement system that also includes ameasurement device configured for estimating or measuring a size of oneor more elements of the measurement device, either by eye or using adigitized image and analysis software or algorithms.

In certain embodiments, the size indicator is an angle indicator. Asused herein the term “angle indicator” is a size indicator in which anangle between two elements or arms of the angle indicator may beobserved, estimated, or measured in order to determine a size of theangle indicator itself and/or a size or other property of a capsular bagor other part of an eye into which the angle indicator is placed.

FIG. 1 is a flow chart of an exemplary method 10 for using an angleindicator for replacing a lens in the capsular bag of an eye.

In element 11, a lens is removed from a capsular bag of an eye. Theremoved lens may be the natural crystalline lens of the eye, which mayhave become opaque due to cataracts or become damaged by some otherdisease or injury. Alternatively, the removed lens may be an existingintraocular lens that is being replaced. Typically, the lens is removedin a surgical procedure in which the lens is broken up and vacuumed outof the eye. The capsular bag, which supports the lens before removal, isgenerally retained for support of the replacement lens.

The replacement lens may be an intraocular lens, such as anaccommodating intraocular lens, which relies on forces transferred bythe zonular fibers in the eye to the capsular bag and/or on forcesproduced by a resiliency of the capsular bag itself. These forces canchange the power and/or location of the lens by change the lens shapeand/or translating one or both of the lens surfaces. The ocular forceexerted by the ciliary muscle, capsular bag, and/or zonular fibers isgenerally limited, and typically the accommodating intraocular lens isdesigned to use this limited force to change power to cover all or partof a desired range of accommodation for the eye. As a result, theintraocular lens may be quite sensitive to compressive or expansiveforces applied to its equator. Importantly, a particular accommodatingintraocular lens may be designed to work optimally for a specificcapsular bag size or size range. If the patient's capsular bag is largeror smaller than expected, the intraocular lens may experience a shift innominal power, or a truncation of the accommodation range, which may beundesirable. Accordingly, it may be useful during a surgical procedureto accurately measure the size of the capsular bag, so that anintraocular lens may be selected for implantation that corresponds tothe actual size of the capsular bag or provides a predetermined fitwithin the capsular bag.

In element 12, an angle indicator, is inserted into the capsular bag.During insertion, it is often desirable to use as small an incision aspossible, so the angle indicator may optionally be inserted in a foldedstate.

In element 13, the angle indicator is expanded to coincide with a sizeor diameter of the capsular bag. If the angle indicator is inserted in afolded state, it may be first unfolded to reach its full size. Thecapsular bag material is flexible, so that it may be bent and reshaped.It may be relatively straightforward to position the angle indicator,which may be generally ring-shaped, along the equator of the capsularbag. Typically, some gentle, back-and-forth motions applied by thesurgeon are sufficient to move the angle indicator to lie along theequator of the capsular bag. In general, the shape of the empty capsularbag is such that it may be well-approximated as circular when viewedfrom the front. Any azimuthal errors in the positioning of the angleindicator generally do not significantly affect the angular reading fromthe angle indicator, or the measured value for the capsular bag size.

In element 14, once the angle indicator is aligned along the equator ofthe capsular bag, the angle is read from the angle indicator. The anglemay be formed from the intersection of two generally straight elementson the angle indicator. In some embodiments, the intersection issubstantially centrally disposed within the pupil of an eye into whichit has been placed, for example, to aid in measuring the angle thusformed. Alternatively, the straight elements of the angle indicator maybe relatively long (e.g., to provide a predetermined sensitivity),wherein the intersection between the two generally straight elements maybe near the edge of the pupil or outside the pupil. The angle may beseen visually by the surgeon or by a camera or microscope trained on thesubject eye. Alternatively or additionally, the angle may be determinedby producing an electronic or digital image of the angle indicator andprocessing the image using software or algorithms to analyze the image.

In element 15, once the angle has been read, the angle indicator may beremoved from the capsular bag of the eye. The angle indicator may befolded upon itself for removal, which is especially convenient if theangle indicator is inserted in the folded state. Alternatively, theangle indicator may be broken or separated into segments, and then thesegment may be removed through the incision in the eye. In oneembodiment, the angle indicator includes cutaways on its posteriorsurface, or other location, which may allow sectioning in vivo forremoval of the angle indicator.

In element 16, the read angle is converted to a capsular bag size orother property of the capsular bag. The size may be reported as adiameter, or, equivalently, as a circumference. The conversion may bedone by reading values off a printed table, by reading values off agraph, by plugging the read angle into a predictive formula, by acomputer, or directly by comparing the angle to a dedicated device.Alternatively or additionally, the location of the capsular bag may bedetermined within the eye, for example, relative to the location of thepupil or the macula.

In element 17, once element 16 has produced a value of the capsular bagsize, an intraocular lens may be selected or otherwise specified (e.g.,the parameters of a custom lens may be specified). The lens selection orspecification may be based in part on the capsular bag size, as well ason other data, such as the required lens power, an available amount ofaccommodative force, and/or a targeted range of accommodation.

For instance, for a given required nominal lens power, there may beseveral intraocular lenses available, each sized for a particularcapsular bag diameter. The available lenses may be part of a kit, withdiameter spacings of 0.5 mm, 0.25 mm, 0.2 mm, 0.15 mm, 0.1 mm, 0.05 mm,or any suitable value. Typically, the exact size value given fromelement 16 may not be exactly available in the kit, and the surgeon orpractitioner may have to round off to the nearest size that is availablein the kit or specify a custom lens.

Alternatively, the intraocular lens may have an adapter that can beattached to the circumference of the lens, which allows a single lens tobe used with multiple sizes of capsular bags.

As a further alternative, the intraocular lens may itself be adjustable,for instance, with an adjustable haptic that can couple a particularoptic to a capsular bag sized within a particular range.

In element 18, once an intraocular lens is selected from element 17, theselected lens may be surgically implanted in the capsular bag.

Note that element 15 follows element 14, and elements 16 and 17 followelement 14, but elements 16 and 17 need not follow element 15. Forinstance, element 15 may follow element 17, which follows element 16,which follows element 14. The conversion of the read angle to a capsularbag size and the selection of a lens based on the capsular bag size areessentially independent of removal of the angle indicator from thecapsular bag, and these elements may be performed in any suitable order.

Referring to FIG. 2, an angle indicator 30 suitable for use with themethod 10 is shown. The angle indicator 30 comprises a broken ring orincomplete annulus 31, with the broken portion of the ring replaced bytwo arms, segments, or straight sections 32 and 33 that connect to thebroken ring 31 and are hingedly connected to each other at a locationwithin the interior of the broken ring 31. The angle indicator isinserted into the capsular bag and the ring 31 expands until it iscoincident with a diameter of the capsular bag. As the ring itselfexpands and contracts, the angle between the two segments increases anddecreases. The angle indicator 30 is generally configured to provide anindication or measurement of a capsular bag size or other propertyindependent, or at least substantially independent, of corneal or cameramagnifications. The size indicator 30 extends into the center of thecapsular bag and is compliant, so that it may be safely removed bygrasping the central features and withdrawing it from the capsular bag.Additionally or alternatively, the size indicator 30 may be used forsizing other portions of the eye such as the sulcus or anterior chamberof the eye. The shape or shape change may be measured visually by eye,with or without the use of an external gauge or template, or may bemeasured using a camera and associated image processing software.

With additional reference to FIG. 3, the angle indicator 30 is designedso that a relatively small change in diameter of the ring 31 produces arelatively large change in angle between arms 32, 33. For instance,three exemplary diameters D1, D2 and D3, are shown in FIG. 3, along withtheir corresponding angles A1, A2 and A3. The relationship betweenmeasured angle and ring (and, therefore, capsular bag) diameter is shownin the exemplary plot in FIG. 3. Note that the relationship need not betruly linear, as shown in FIG. 3, but may have any suitable increasingrelationship, such as a quadratic or more complex polynomialrelationship. During use, the practitioner inserts the angle indicator30 into the capsular bag, expands the angle indicator 30 to fill thecapsular bag, reads the angular value from angle indicator 30, andconverts the read angular value to a capsular bag diameter, orequivalently, circumference.

Note that the angle is viewable near the center of the pupil of thelens, rather than only at the edge of the pupil or the edge of thecapsular bag. This reduces the need for unusual viewing techniques, orextra handling of the pupil, and may help reduce distortion of the anglewhen viewed through the patient's cornea.

In one embodiment, the angle indicator 30 remains substantially round,for all angles/diameters within a particular range. This is accomplishedby varying the radial thickness of the ring, with a maximum thicknessopposite the two segments, and a minimum thickness in the regionsadjacent to the joints that attach the straight segments to the rest ofthe ring. This is shown more clearly in FIG. 2.

The incomplete annulus 31 of the angle indicator 30 may optionally havea varying radial thickness around its circumference. Adjacent to thehinges 34 and 35, the radial thickness 36 may be its minimum. The radialthickness may increase farther away from the hinges 34 and 35, reachingan intermediate value 37 partially around the ring, and may finallyreach a maximum value 38 directly opposite and between the hinges 34 and35. Alternatively, the radial thickness may be constant around itscircumference, or may vary in a manner other than the exemplary mannerdescribed above.

In the exemplary design of FIG. 2, the out-of-plane thickness isessentially constant along the incomplete annulus 31 and segments 32 and33. The corners may be rounded, or may be un-rounded.

The variation in radial thickness around the ring helps ensure that theincomplete annulus stays essentially round, even as the angle betweenthe straight segments 32 and 33 varies. As such, the diameter dimensionsD1, D2 and D3 in FIG. 3 are truly diameters, and the outermost shapes ofthe angle indicators are essentially round at each of the three sizesshown. The angle indicator 30 retains its round periphery as it iscompressed.

Alternatively, the radial thickness of the angle indicator 30 may remainessentially constant around the ring, and the out-of-plane thickness mayvary along the ring. As further alternatives, both the radial thicknessand the out-of-plane thickness may vary around the ring and/or theradial thickness may remain constant but the material modulus orstrength may vary along the ring, for example, being stiffer away fromthe hinges.

The hinges 34 and 35 may be formed integrally as weakened portions ofthe angle indicator 30. In one embodiment, the hinges 34 and 35 areformed at regions of reduced in-plane thickness at the intersections ofthe straight segments 32 and 33 with the incomplete annulus 31. As such,the hinges 34 and 35 may bend freely in the in-plane direction, allowingthe angle indicator to freely expand and contract to attain its maximumsize inside the capsular bag. The hinges 34 and 35 may be configured topreclude or reduce movement of the two segments 32, 33 out of the planeof the angle indicator 30. Generally, the angle indicator 30 may be madeintegrally as a single unit, or may be made from several pieces that areassembled. The assembled pieces may be made from the same or fromdifferent materials.

The segments 32, 33 are joined to each other by a third hinge 39, formedby an in-plane thickness reduction, also permits free in-plane movementof the segments 32, 33 with respect to each other. The helps to providefree diametric expansion and compression of the angle indicator 30 andrestricts out-of-plane movement.

Note that the segments 32 and 33 are shown in the figures as beingentirely straight. In practice, there may be some curvature to all or aportion of either or both of the segments. For instance, there may besome local waviness to all or a portion of the segments 32 and 33.Alternatively, there may be a more global curvature, having a radius onthe order of or larger than the angle indicator radius. In oneembodiment of the angle indicator, the segments 32 and 33 are straightthroughout.

Note that the angle indicator 30 may measure capsular bags having a sizelarger than the incision through which the angle indicator is inserted.For instance, the angle indicator may measure capsular bag diameters onthe order of 11 mm. In general, the diameter of the angle indicator inan uncompressed state is at least about 9 millimeters in diameter, butmay be between about 8 millimeters and about 15 millimeters, preferablybetween about 9 millimeters and about 12 millimeters. In someembodiments, the diameter of the angle indicator in an uncompressedstate has a nominal value of 11 mm or about 11 mm (i.e., 11 mm plus orminus 0.5 mm). As such, the angle indicator 30 may be compressed in aninjector or folded upon itself during insertion (and later, duringextraction), and may be unfolded and expanded for performing themeasurement. When used in conjunction with an accommodating intraocularlens, the angle indicator is configured to fit through an incision inthe eye that is less than about 5 millimeters, preferably less than 4millimeters. In other embodiments, for example when used with anintraocular lens that does not provide accommodation, the angleindicator is configured to fit through an incision in the eye that isless than about 3 millimeters, preferably less than 2 millimeters.

During insertion and positioning of the angle indicator 30, it may bebeneficial to gently “force open” the straight segments 32 and 33 of theangle indicator 30. This may be accomplished by applying a force on ornear the rear (essentially flat) side of the hinge 39, directed outwardfrom the ring, toward the opening between the segments. The force may beapplied by the practitioner using the equipment that is typically usedto position objects during surgery, such as a hook or forceps. Becausethe force may be applied directly to angle indicator 30, there may be noneed for extra holes or tabs for this purpose, although holes and/ortabs may optionally be used.

In certain embodiments, the angle indicator 30 is configured to producea relatively small force when placed within a capsular bag. For example,the force produced by the angle indicator 30 when the diameter iscompressed 2 millimeters may be between about 0.5 gram and about 20grams, preferably between about 0.5 gram and 5 grams. Such low forcesmay beneficially reduce the possibility of damaging the capsular bagduring use of the angle indicator 30, but may require manipulation bythe practitioner to insure that the incomplete annulus 31 fully engagesthe equatorial region of the capsular bag. Alternatively, a higher forcemay be used to ensure positive engagement of the equatorial region ofthe capsular bag with a minimal amount of adjustment by a practitioner,for example, a force of between about 10 grams and about 30 grams ormore.

The length of the segments 32 and 33 may be varied, so that the hingethat joins them may fall on either side of the center of the ring at itsnominal position. As the segment length is increased, the angle becomeseasier for the practitioner to read during use, although the sensitivityis decreased. Likewise, as the segment length is decreased, the anglebecomes more difficult for the practitioner to read during use, but thesensitivity is increased. In practice, the designer of ordinary skill inthe art understands this trade-off, and may design an angle indicator 30with a suitable range of operation, a suitable sensitivity, and asuitable ease of angle viewing.

Optionally, there may be more than one angle indicator for a particulareye or patient, with each angle indicator covering a particular range ofcapsular bag sizes. For instance, one angle indicator may be used forcapsular bag diameters in the range of 9 to 10 mm, and another angleindicator may be used for the range 10 to 11 mm. These values are merelyexemplary, and any suitable ranges may be used.

Note that because the angle may be measured from roughly the center ofthe pupil, there is generally little distortion of the angle caused bythe cornea. If the cornea imparts a magnification an image of thesegments forming the angle, the segments themselves may appear to growor shrink in size, but the angle between the segments remainsessentially unchanged. This holds for a wide range of cornea radii, anda wide range of magnifications caused by the cornea.

It is instructive to perform some trigonometry to more accurately showthe graphical dependence of measured angle A and capsular bag diameterD, which is not truly linear as shown schematically in FIG. 3, but has amore complicated dependence.

FIG. 4 shows an exemplary geometry for one embodiment of an angleindicator. We assume for this simplistic analysis that the lengths ofthe incomplete annulus (i.e., the open ring-shaped segment) and thestraight segments remain constant during use; this is a goodapproximation for this purpose.

Both the length of the incomplete annulus and the length of eachstraight segment may be related to a “closed diameter” D₀, which is thediameter of the angle indicator when the segments are parallel, or“closed”. The length of the incomplete annulus is πD₀, and the length ofeach straight segment is qD₀, where q is a dimensionless quantity thancan between 0 and 1. When q is 0.5, the straight segments extend toexactly the center of the ring when the ring is “closed”. When q is 1,the straight segments extend all the way to the opposite end of the ringwhen the ring is “closed”. When q is 0, the straight segments areinfinitesimally small.

During use, the angle indicator expands to a diameter of D, with ameasured angle A between the straight segments. Length y and angle A aremathematical constructs. We attempt to solve for A in terms of D.

First, solve for y: y=D sin(A/2).

Next, we express angle A in terms of the length πD₀ of the incompleteannulus: A=(2π−2πD₀/D).

Plug into expression for y: y=D sin(π−πD₀/D)=D sin(πD₀/D)

Can also solve for y in terms of A and qD₀: y=2 qD₀ sin(A/2)

Set these two expressions for y equal to each other and rearrange toget: sin(A/2)=sin(πD₀/D)/(2 qD₀/D)

Solve for A and rewrite as A=2 sin⁻¹([π/2q]×[sin(πD₀/D)/(πD₀/D)])

FIG. 5 is a graph of the above equation, which predicts capsular bagdiameter D versus measured angle A, for several values of q.

The choice of q is related to both sensitivity and dynamic range. Forrelatively short straight segments (low q), there is high sensitivityand low dynamic range. Similarly, for relatively long straight segments(high q), there is low sensitivity and high dynamic range.

In some embodiments, it is preferable if the vertex, or intersectionbetween the straight segments, is located at or near the center of thering for at least part of the range of use. The circles superimposed onthe various plotted curves in FIG. 5 show the operating condition atwhich the vertex is at the center of the ring. Note that for shortsegments (q<0.5), there is no condition under which the vertex can belocated in the center of the ring; these segments are just too short toextend to the center, regardless of angle A.

Note that for q=0.6 (i.e., where the straight segments are 20% longerthan the radius of the “closed” ring), the vertex falls at the center ofthe ring at a measured angle A of 60 degrees. In one embodiment, thismay be a preferable set of conditions; the plotted region for q=0.6 isenlarged and is shown in FIG. 6.

For FIG. 6, we choose a convenient set of numbers, which are merelyexemplary and are not intended to be limiting in any way. For instance,if we wish to measure capsular bags having a diameter in the range of 11mm to 13 mm, we use an angle indicator having a “closed” diameter of 10mm and a short segment length of 6 mm, and detect angles between 30 and90 degrees. If our detection scheme allows us to detect angle A to thenearest 15 degrees, we may measure the diameter of the capsular bag tothe nearest 0.5 mm (based on the 10 mm diameter of the angle indicator).These values are merely exemplary, and any lengths and diameters may bescaled upwards or downwards. Other suitable values may also be used.

Note also that the mathematical analysis that generates the plots ofFIGS. 5 and 6 is approximate, and assumes that the lengths of thering-shaped segments and the two straight segments all remain constantthroughout operation. This is only an approximation, and one of ordinaryskill in the art will readily appreciate that more sophisticatedsimulations may be performed that account for local stresses anddeformations, bending of the materials, and other effects not consideredin the simplistic analysis presented above.

The discussion thus far has focused primarily on the angle indicator 30,which generates an angle as a function of the capsular bag size orshape. The following paragraphs focus primarily on measurement devicesfor estimating or measuring the angle between arms 32, 33 of the angleindicator 30 or other size indicators. For the purposes of thisdocument, the term “measurement device” means any device or systemsuitable for measuring or estimating a size or location of a sizeindicator or angle indicator disposed within an eye, for example, bymeasuring or estimating an angular or linear dimension of one or moreelements of the size indicator or angle indicator. The measurementdevice may, for example, be a sizing gauge, an image processing system,software package, or the like. The measurement device may includesoftware, hardware, firmware, or algorithms suitable for providing ameasurement or estimate of a size or location of a size indicator orangle indicator.

For the purposes of this document, the term “sizing gauge” means aphysical measurement device suitable for providing an estimate ormeasurement of a size or location of a size indicator or angleindicator. For example, a sizing gauge may be a template, chart, set ofreference images, reticle, protractor, or the like. In certainembodiments, a sizing gauge includes a flexible sheet that may be placedon the eye (e.g., a contact lens) having marks configured for measuringor estimating a dimension of a size indicator or angle indicator. Inother embodiments, a sizing gauge may include a calibrated reticle orprotractor, which may be used for visual inspection by eye, or used withan optical instrument, such as a microscope or a camera. When used withthe angle indicator 30, or similar device, the sizing gauge may includeangular increments on the reticle or protractor may include one halfdegree, one degree, five degrees, 10 degrees, 15 degrees, 20 degrees, 25degrees, 30 degrees, 35 degrees, 40 degrees, 45 degrees, or any suitableincrement. Alternatively, the sizing gauge may be marked with indiciathat correspond directly to the capsular bag size or appropriate rangescorresponding to available implant sizes. As used herein, the term“protractor” means a device that can read, measure, or indicate an angleof a size indicator or angle indicator, either by visual inspection orby electronic means.

An exemplary protractor 70 for use with the angle indicator 30, oranother size indicator for sizing a capsular bag, is shown in theisometric drawing of FIG. 7 and the three views of the plan drawing ofFIG. 8.

The protractor 70 has a generally circular ring 71 that is sized to reston the cornea to allow measurement of the angle from the angleindicator. The ring 71 is small enough to fit on the eye of the patient,and large enough to surround the pupil of the eye. A typical range ofdiameters for the protractor ring may be from about 3 mm to about 12 mm,or from about 5 mm to about 8 mm.

Note that the straight segments 32 and 33 of the angle indicator 30 areviewable from roughly the center of the pupil, rather than requiring ameasurement taken at the edge of the capsular bag. As a result, ring 71of the protractor need not extend all the way to the edge of thecapsular bag or to the edge of the cornea. The ring 71 may optionallyhave rounded or chamfered edges that may reduce the risk of scratchingthe cornea.

The protractor 70 has a reference portion 72 that has radial edges 73and 77. During use, the reference portion 72 generally extends out ofthe plane of the ring 71, so that it may rest upon or extend over thecornea, which is curved. When viewed from the front, the intersection ofradial edges 73 and 77 may fall at or near the center of the ring 71,and/or at the intersection of the straight segments 32 and 33 (e.g., atthe hinge 39). Note that the reference portion 72 may deform so thatthis intersection of radial edges 73 and 77 may lie away from the centerwhen the protractor is not in use.

In one embodiment, the protractor is rigid, so that the protractorroughly maintains its shape before, during and after use. In thisembodiment, the reference portion 72 may extend out of the plane of thering 71 in its relaxed state before use. Alternatively, the referenceportion may 72 may be located roughly in the plane of the ring 71 beforeuse, and may pivot in the anterior direction during use. The pivotingmay occur around a weakened portion of the reference portion, which mayinclude an optional hole, opening, or void area 81. In some embodiments,the void area 81 may have a more complex shape that the hole shown inFIG. 7, for example, to provide a weakened zone with predeterminedbending characteristics or to avoid confusion that the void area 81represents an alignment mark with the straight segments 32 and 33.

In another embodiment, the protractor 70 is flexible, and may be drapedonto the cornea of the eye. Such a flexible protractor conformsgenerally to the shape of the cornea, without significantly deforming inthe plane of the protractor. The protractor 70 may be made from alargely transparent material, and may include markings or features thatindicate predetermined angle values. For instance, the protractor 70 mayinclude a central feature that may be overlaid with the hinge 39 duringuse, and various angular features, such as reticle marks or other radiallines or features. In one embodiment of a flexible protractor 70, theprotractor may be formed on or be made integral with a contact lens thatis placed onto the cornea during use.

For the protractor 70 of FIG. 7, the protractor is positioned during useso that one of the radial edges 73 and 77 lines up with one of thestraight segments 32 and 33. The other straight segment falls elsewherearound the circumference of the ring, and may fall near one of severalcalibration features, such as notches, tabs, holes, extensions,annotations, colors or members.

For instance, if radial edge 73 is aligned with straight segment 32,then straight segment 33 may fall near one of feature 74, feature 75 orfeature 76. The features may be in calibrated increments, such as 30degrees, 20 degrees, 15 degrees, 10 degrees, 5 degrees, 1 degree orless, or any suitable increment. For instance, if the increment is 30degrees between each of the features 74-76, then if the straight segment32 falls closest to the feature 74, then the angle of the indicator isclosest to 30 degrees. Similarly, if the straight segment 32 fallsclosest to the feature 76, then the angle of the indicator is closest to90 degrees.

In addition, there is a second set of radial edge 77 and features 78-80,which may be used equally as well as the first set of radial edge 73 andfeatures 74-76. The second set may be calibrated with the same angularincrement as the first, or with a different angular increment as thefirst.

Alternatively, there may be more than three or fewer than threefeatures. In addition, the features may be evenly or unevenly spaced.

Once the measurement has been taken, the protractor 70 may be removedfrom the cornea of the patient. In one embodiment, the protractor 70 maybe removed by grasping it with the hole 81, or by an optional elevatedfeature or tab (not shown).

In certain embodiments, a more conventional protractor may be used, withnotches, tick marks, lines, or other visual cues extending around thecircumference at a prescribed interval, such as every 30 degrees, or anyother suitable interval. This more conventional protractor may lack thereference portion 72. As another example, the protractor may be madefrom a soft material that is draped over the cornea or rests on thefacial tissue that surrounds the eye, rather than on the eye itself.Alternatively, the angle may be measured from an image formed of the eyeon a screen or in software. As a further alternative, there may be anangular reticle supplied with a camera or microscope, which may allow areading of the angle.

Both the angle indicator 30 and the protractor 70 may be made from anysuitable biocompatible and flexible materials. For instance, either orboth may be made from silicone or any polymeric material, PMMA, or anyother suitable material. In one embodiment, the material or materialsused may be moldable, and may not be hydrophilic. In one embodiment, thematerial is sterilizable by autoclave, by ETO, or by any suitablesterilization process. The angle indicator 30 and protractor 70 may bemade from the same or from different materials. Either or both angleindicator 30 and protractor 70 may be made of a transparent ortranslucent material. Alternatively, either or both angle indicator 30and protractor 70 may be made of a tinted, opaque or fluorescingmaterial, so that they may easily be read visually. In one embodiment,the angle indicator and protractor may be supplied in pre-sterilized,sealed packages that accompany an intraocular lens. Both the angleindicator and protractor may be unsealed when needed, and disposed ofonce a measurement has been taken.

In other embodiments, either or both the angle indicator 30 and theprotractor 70 may be configured for single-use or a limited number ofuses. For example, the protractor 70 may be made of an autoclavablematerial for reuse in subsequent procedures, while the angle indicator30 is made of a disposable material that is discarded after one use orafter use on a single subject. In such embodiments, the angle indicator30 or a set of angle indicators 30 may be shipped in a sterile conditionalong with an intraocular lens to be inserted into a subject eye.

In one embodiment, there may be sets of angle indicators andprotractors, with each set corresponding to a different range ofcapsular bag sizes. For instance, one set may be used for a size rangeof 9 to 10 mm, and another set may be used for a size range of 10 to 11mm. Each set may be color-coded so that the particular protractor iseasily associated with its corresponding angle indicator, and themeasured angles are easily associated with their proper measuredcapsular bag sizes. Alternatively, there may be other identifyingcharacteristics for matched sets of angle indicators and protractors,such as texture, etching, surface characteristics, ridges and so forth.

In certain embodiments, an electronic or digital image of the angleindicator 30 in the eye and/or the protractor 70 is produced. Thedigital image may be captured and processed using a computer or otherelectronic system in order to determine the angle between the twostraight sections 32 and 33. The resulting digital representation may beused to increase the accuracy of the angle measurement, as a cross-checkto a manual measurement, or to provide other information (e.g., thelocation of the angle indicator and/or capsular bag within the eye, orto determine a change in size of the capsular bag, as discussed ingreater detail below).

In one embodiment, the outer edges of the angle indicator may expandthrough viscoelastic/OVD in the capsular bag.

In one embodiment, the straight segments, or central arms, of the angleindicator may extend past the center of the angle indicator. Theselonger straight segments may fill a larger area of the pupil, and mayprovide an easier measurement than smaller or shorter straight segments.

In one embodiment, the angle indicator may be inserted into the capsularbag by an injector.

In one embodiment, the angle indicator may include a tether, so that theangle indicator may be more easily withdrawn after the measurement hasbeen taken. The withdrawing may be done directly by the tether.Alternatively, the tether may attach the angle indicator to an injector,so that the withdrawal may be done by the injector.

In one embodiment, the angle indicator may include one or more loops onthe straight segments or on the incomplete annulus that extend in theanterior direction (i.e., away from the patient's eye), for positioningand removal of the angle indicator.

In one embodiment, the flexural characteristics of the straightsegments, or arms, their bases, and/or the central hinge may be “tuned”in shape or stiffness, so that the angle indicator may stay round over awide range of compression.

In certain embodiments, the angle indicator 30 is made of a siliconematerial having a hardness of between about 70 durometer and about 80durometer which approximately corresponds to a modulus of elasticitythat may provide a desired compressive force when the angle indicator isplaced within a capsular bag. In other embodiments, the modulus ofelasticity of the angle indicator material (e.g., silicone or acrylic)and/or the width of the various angle indicator sections may be varied,so that reliable measurements may be made without excessively stretchingthe capsular bag.

In certain embodiments, the angle indicator 30 may be used to determineor estimate the resiliency of the capsular bag into which it isimplanted. For example, the angle indicator 30 may be made of a materialhaving a relatively high modulus of elasticity and/or may be otherwiseconfigured to be relatively resilient or stiff. In some embodiments, twoor more angle indicators 30 may be used. For example, a first angleindicator 30′ may be inserted into the capsular bag that produces arelatively low force on the capsular bag (e.g., between about 0.1 gramto about 10 grams of force). As such, the first angle indicator 30′ maybe used to determine the size of the capsular bag when in asubstantially unstressed state, as described in greater detail above.The first angle indicator 30′ may then be removed from the eye andreplaced by a second angle indicator 30″ that is stiffer than the firstangle indicator 30′, thus producing a higher, radially outward force(e.g., in the range of about 5 grams to about 30 grams or more) whencompressed by about the same amount as the first angle indicator 30′.Due to the increased force on the capsular bag, the bag is stretched bythe second angle indicator 30″ and thus produces a different bag sizemeasurement. In some embodiments, the second angle indicator 30″additionally or alternatively has a diameter that is greater than thefirst angle indicator 30′, thereby increasing the force produced on thecapsular bag compared to that produced by the first angle indicator 30′.Other differences between the angle indicators 30′, 30″ may beadvantageously used to provide a different radially outward force and/orto determine the resiliency of the capsular bag.

Alternatively, a single angle indicator 30 may be used that remains inthe capsular bag; however, the size of the angle indicator 30 and/or onthe capsule wall may be changed by increasing or decreasing the radiallyoutward force of the incomplete annulus 31 or exerted on the incompleteannulus 31. The change in force may be produced by changing theresiliency of the angle indicator 30 and/or by inserting another deviceor apparatus that applies additional force on the equatorial region ofthe capsular bag and/or angle indicator 30. In some embodiments, asurgeon may change the outward force on the incomplete annulus 31 byusing one or more probes or other devices to push or pull at one or morelocations on the incomplete annulus 31.

However the difference in size is induced, the resulting size differencemay be measured and used to calculate a resiliency of the capsular bagand/or estimate the amount of accommodative force available foraccommodation. In some embodiments, the change is size is quantitativelymeasured to determine a resiliency or other property of the capsularbag. Alternatively, the change in size may be qualitatively assessed sothat the surgeon may broadly characterize a resiliency or other propertyof the capsular bag.

In certain embodiments, the angle indicator 30 is implanted within acapsular bag and the force produced by the ciliary muscle is changed inorder to measure a change in the size and/or amount of force produced bythe capsular bag. For example, a muscarinic agent such as a muscarinicagonist or a muscarinic antagonist may be used to alter the amount ofaccommodative force produced by the eye, as disclosed in U.S. Pat. No.6,598,606 or US Patent Application Number 2005/0251254, which are hereinincorporated by reference.

In one embodiment, a plurality of angle indicators 30 is provided in theform of a kit, with each angle indicator 30 having a differentelasticity or tensile strength. Such a kit may be used to determine theelasticity of a particular evacuated capsular bag, in order to bestdetermine the most compatible accommodating intraocular lens.

In one embodiment, the angle indicators 30 are provided in a kit, witheach angle indicator 30 having a different axial thickness. Such a kitmay help match the measurement of the capsular bag size to the axialthickness of the intended implanted intraocular lens, both at the edgeof the lens and centrally.

In one embodiment, the arms 32, 33 include overlapping, curved vernierextensions. With reference to the exemplary design of FIG. 2, arm 32 mayinclude one or more tangentially-curved extensions that protrude towardarm 33, and arm 33 may also include one or more tangentially-curvedextensions that protrude toward arm 32, with the tangentially-curvedextensions being located next to each other. In this manner, the anglemay be read directly from the extensions, rather than with an additionalexternal device such as a measurement device or sizing gauge.

In one embodiment, the incomplete annulus 31 may include extensions ortabs protruding from one or both of the straight segments 32, 33 anddisposed along the circumference of, and in the plane of, the incompleteannulus 31. These optional extensions may help maintain the capsularcircularity in the region between the straight segments 32, 33.

In addition to measuring the capsular bag size for intraocular lensimplantation, the angle indicator 30, or variations thereof, may be usedfor other fields as well, such as measuring the diameters and stenosisof body cavities, especially in endoscopic and catheter-based proceduresfor sizing shunts and implants. The angle indicator allows estimation ofa particular diameter, regardless of viewing magnification. This mayalso be used in the fields of interventional cardiology, as well asvascular, bariatric and gastroenteric surgeries. Furthermore, the angleindicator 30, or variations thereof, may also be used to measure thesize of the anterior chamber or other cavities of the eye.

Referring to FIGS. 9-11, in some embodiments, a sizing gauge 102 isconfigured for measuring or estimating a size of a size indicator (e.g.,the angle indicator 30) or for measuring or estimating a size or othercharacteristic of a capsular bag or other cavity into which a sizeindicator is inserted. Where applicable, the sizing gauge 102incorporate features and functions of the protractor 70 discussed above,or visa versa.

In the illustrated embodiments in FIG. 11, the sizing gauge 102 is partof a measurement system comprising an angle indicator 90 and the sizinggauge 102, the system configured for measuring a size or othercharacteristic of a capsular bag of an eye. The angle indicator 90 maybe similar or equal to the angle indicator 30. The angle indicator 90includes a peripheral portion 92 configured to contact a capsular bag ofa subject eye and a pair of arms 94 operably coupled to the peripheralportion 92 and joined at an intersection of the arms 94. The arms 94 areconfigured so that an angle formed by the arms 94 varies in response toa size of the capsular bag and/or other property, such as a resiliencyor elasticity of the capsular bag.

The sizing gauge 102 comprises a body 110 having a front surface 112.Various features of sizing gauge 102 are visible when viewed from infront of the front surface 112, these features being useful formeasuring an angle of the angle indicator 90 or similar device. Any orall of these features may be disposed on the front surface 112 and/or ona surface of the sizing gauge 102 that is opposite the front surface112. Alternatively, at least some of the features may be disposedbetween front and back surfaces of the sizing gauge 102, for example, ona laminate surface that is between front and back surfaces of the sizinggauge 102.

In the illustrated embodiment, the sizing gauge 102 includes an innerportion 115, an outer portion 118, and a border or boundary 120 disposedtherebetween. The boundary 120 is configured to provide a comparison,estimate, or measurement of an angle of the arms 92 of the angleindicator 90 when the sizing gauge 102 is disposed in front of the angleindicator 90.

Optionally, the sizing gauge 102 may comprise a handle or grip 128, asillustrated in FIG. 10 for the sizing gauge 102′. The handle 128 may besized and configured to allow the sizing gauge 102′ to be held by apractitioner in order to move the sizing gauge 102′ into a desiredlocation and orientation in front of the angle indicator 90.Additionally or alternatively, the handle 128 may be configured to beheld by a robotic or automated positioning device that is controlledeither by an electronic controller configured to move the sizing gauge102 relative to the angle indicator 90.

The sizing gauge 102, 102′ may be made of a metal or polymer material,or any material suitable for a clinical environment and providingnecessary physical properties. The sizing gauge 102, 102′ may be made ofa single material or may comprises different materials. For example, thehandle 128 of the sizing gauge 102′ may be made of a different materialthan the rest of the sizing gauge 102′. In some embodiments, all orportions of the sizing gauge may be made of a transparent orsubstantially transparent material, for example, in order to facilitateviewing of the angle indicator 90 when used therewith.

The inner portion 115 may be an opening or aperture 124 in the body 110,wherein the boundary 120 is an inside edge of sizing gauge 102. In suchembodiments, the outer portion 118 may be made of either a transparentmaterial or an opaque material. The aperture 124 and the boundary 120are configured to allow the angle between the pair of arms 94 of theangle indicator 90 to be estimated or measured.

In some embodiments, the inner and outer portions 115, 118 are made of acommon or similar material, wherein the boundary 120 is a border betweenthe portions 115, 118. In such embodiments, the inner and outer portions115, 118 may both be made of a transparent, semi-transparent, or clearmaterial, wherein the border 120 may be dark, opaque, or otherwiseconfigured to allow delineation between the inner and outer portions115, 118. Alternatively, at least one of the portions 115, 118 may beopaque, colored, translucent, frosted, darkened, or only partiallytransparent, while the other portion 118, 115 may transparent orsemitransparent.

The border 120 in the illustrated embodiments comprises a quadrilateralshape 125 in which opposite vertices 126 a, 126 b join sides of thequadrilateral to form angles that are different from one another, theangles being selected to correspond different angles between the pair ofarms of the angle indicator 90. The sizing gauge 102, 102′ may furthercomprise alphanumeric characters 130, for example, in the inner or outerportions 115, 118 and/or indicating a size or other value correlating toone or more angles of the angle indicator 90.

During use one of the vertices 126 a, 126 b is aligned to a vertex ofthe angle indicator 90 located at the intersection of the arms 94. Asillustrated in FIG. 11, the angle between the sides forming the vertex126 b is approximately equal to the angle formed by the arms 94 of theangle indicator 90. The alphanumeric “10 mm” near the vertex 126 bindicates that the match or approximate match between these two anglescorrelates to a capsular bag diameter of 10 mm or approximately 10 mm.Alternatively, the alphanumeric characters on the sizing gauge 102 maybe used to indicate or correlate to other quantities such as, an anglebetween the pair of arms of the angle indicator 90, a circumference,cross-sectional area, or volume of the capsular bag, a resiliency of thecapsular bag, or the like.

The outer portion 118, inner portion 115, surface 112, and/or the backsurface opposite surface 112 of sizing gauge 102, 102′ may be eitherplanar or curved. If curved, the radius of curvature may be selected toallow the sizing gauge to be draped over the cornea of an eye. Forexample, the sizing gauge 102 may be a contact lens that has a radius ofcurvature that is approximately equal to the radius of curvature of thecornea. Alternatively, the surface curvature of the sizing gauge 102′may be configured to fit or closely fit the shape of the cornea. In anyevent, the sizing gauge 102, 102′ may be configured to have little or nooptical power. Alternatively, the sizing gauge 102, 102′ may beconfigured to have an optical power, for example, a negative opticalpower that at least partially compensates or nullifies the optical powerof the cornea of an eye. In other embodiments, the optical power isselected to provide a desired magnification or to form part of animaging system configured to view the angle indicator 90 or a portion ofthe eye into which the angle indicator 90 is implanted.

In some embodiments, a kit comprising a plurality of sizing gauges 102is provided, for example, with each sizing gauge 102 have a differentradius of curvature or shape. Additionally or alternatively, the kit mayinclude a plurality of sizing gauges 102, wherein different sizinggauges 102 have different included angle between the sides of the innerportion 115.

Referring to FIGS. 12 and 13, in some embodiments, a sizing gauge 202 isconfigured for measuring or estimating a size of a size indicator (e.g.,angle indicators 30, 90) or for measuring or estimating a size or othercharacteristic of a capsular bag or other cavity into which a sizeindicator is inserted. Where applicable, the sizing gauge 202incorporate features and functions of the protractor 70 and/or thesizing gauges 102, 102′ discussed above, or visa versa. In theillustrated embodiments in FIG. 13, the sizing gauge 202 is part of ameasurement system comprising the angle indicator 90 and the sizinggauge 202, the system being configured for measuring a size or othercharacteristic of a capsular bag of an eye.

The sizing gauge 202 comprises a body 210 having a front surface 212 andvarious features that are visible when viewed from in front of the frontsurface 212, these features being useful for measuring an angle of theangle indicator 90 or similar size indicator. Like the sizing gauge 102,the features of the sizing gauge 202 may be disposed on one or more ofthe front or back surfaces of the sizing gauge 202, or between the frontand back surfaces.

The sizing gauge 202 comprises a first feature 224 and a second feature226 that are disposed on or behind the surface 212. The first feature224 is a vertex mark 224 that is configured to be aligned to the vertexof the angle indicator 90 formed at the intersection of the arms 94. Inthe illustrated embodiment, the vertex mark 224 comprises an aperturethat may be a through hole in the body 210 or may comprise a clearmaterial, for example, the same material as the remaining portions ofthe body 210. Alternatively, the vertex mark 94 comprises a pair ofcrosshairs, a bull's eye pattern, or other marking suitable forfacilitating alignment of the sizing gauge 202 to the intersection ofthe arms 94 of angle indicator 90.

The second feature 226 of the sizing gauge 202 comprises three linesthat are disposed parallel to one another and perpendicular to alongitudinal axis of the sizing gauge 202. In other embodiments, thesecond feature comprises a different number of lines (e.g., 2 lines or 4lines). In any event, the lines 226 are disposed a different distancesfrom the vertex mark 224 and may have different lengths, as in theillustrated embodiment shown in FIG. 12. The endpoints of each line 226and the center of vertex mark 224 are configured to correspond todifferent angles between the arms 94 of the angle indicator 90.

Referring to FIG. 13, during use, the vertex mark 224 of the sizinggauge 202 is aligned to an intersection between arms 94 of the angleindicator 90. The angle of between the arms 94 may be determined orestimated based upon which of the line 226 endpoints touches, or isclosest to touching, a predetermined part of the arms 94 (e.g., an inneror outer edge of each of the arms 94). In this manner, the measured orestimated angle between the arms 94 may be correlated to a size or otherproperty of the capsular bag into which the angle indicator 90 has beenplaced. In the illustrated embodiment, alpha numeric characters 230 aredisposed near the lines 226 to show a correspondence of the lines 226 toa capsular bag size of either 9.5 mm, 10 mm, or 10.5 mm. It is notnecessary that each line be associated with a particular alphanumericcharacter 230. For example, in FIGS. 13 and 14 the sizing gauge 202 doesnot have an alphanumeric symbol associated with the center line 226, butit is understood that if the arms of the angle indicator just touch thecenter line 226, then this correlates to a capsular bag diameter of 10mm.

Referring to FIG. 14, in some embodiments, a sizing gauge 302 isconfigured for measuring or estimating a size of a size indicator (e.g.,angle indicators 30, 90) or for measuring or estimating a size or othercharacteristic of a capsular bag or other cavity into which a sizeindicator is inserted. Where applicable, the sizing gauge 302incorporate features and functions of the protractor 70 and/or thesizing gauges 102, 102′, 202 discussed above, or visa versa. In theillustrated embodiments in FIG. 14, the sizing gauge 202 may be part ofa measurement system that comprises the angle indicator 90 and thesizing gauge 302, the system being configured for measuring a size orother characteristic of a capsular bag.

The sizing gauge 302 comprises a body 310 having a front surface 312 andvarious features that are visible when viewed from in front of the frontsurface 312, these features being useful for measuring an angle of theangle indicator 90 or other size indicator. Like the sizing gauges 102,102′, 202, the various features of the sizing gauge 302 may be disposedon one or more of front or back surfaces of the sizing gauge 202, orbetween the front and back surfaces. The body 310 of the sizing gauge302 may be made of a clear, colored, frosted, or opaque material,according to the requirements of the user or manufacturer.

The body 310 comprises a pair of notches or wedge-shaped features 324disposed along side and top edges of the body 310. The use of twowedge-shaped features 324 may be configured to allow easy manipulationof the sizing gauge 302 in order to align one of the wedge-shapedfeature 324 to the arms 94. In the illustrated embodiment, eachwedge-shaped feature 324 has the same angular extent—in this case bothangles corresponding to a capsular bag size of 10.8 mm. Alternatively,each of the wedge-shaped features 324 may have a different angle betweenthe edges of the wedge-shaped feature, for example, to facilitatemeasurement of different arm 94 angles with a single sizing gauge 302.In some embodiments, the sizing gauge 302 comprises only onewedge-shaped feature 324. In other embodiments, the sizing gauge 302comprises three wedge-shaped features 324 or more than threewedge-shaped features 324.

The sizing gauge 302 in the illustrated embodiment comprises anelongated body 312; however, other shapes may be used. For example, two,three, four, or more wedge-shaped features 324 may be configured on acircular body, wherein each of the wedge-shaped features 324 has adifferent angle between the edges of the wedge-shaped features 324.

Referring to FIGS. 15 and 16, the sizing gauge 302 may be part of a kitor set 300 or 300′ of sizing gauges 302 that are used for estimating ormeasuring the size or other property of a capsular bag. The sizinggauges 302 in the set 300′ are attached together at a proximal end ofeach sizing gauge 302, for example, to facilitate easy selection betweenindividual gauges 302 during use.

During use, the angle indicator 90 is disposed within the capsular bagof an eye or inside another portion or cavity of the eye. One of thesizing gauges 302 of the kit 300 or 300′ is then selected and located infront of the angle indicator 90 or other size indicator. The sizinggauge is next aligned to the angle indicator 90 so that a vertex 330(see FIG. 14) of the wedge-shaped features 324 is disposed at theintersection of the pair of arms 94 of the angle indicator 90, and sothat at least one of the edges of the wedge-shaped feature 324 isaligned to at least one edge of one of the arms 94. An assessment canthen be made as to whether or not the angle of the wedge-shaped featureis sufficiently close to the angle between the arms 94. If so, then theangle may be correlated to a size of the angle indicator or a size orother property of the capsular bag into which the angle indicator 90 hasbeen placed. If the angles do not match, then another sizing gauge 302from the kit 300, 300′ is selected and the process is repeated until acorrespondence is found between the angle of the wedge-shaped feature324 and the angle between the arms 94 of the angle indicator 90.

The description of the invention and its applications as set forthherein is illustrative and is not intended to limit the scope of theinvention. Variations and modifications of the embodiments disclosedherein are possible, and practical alternatives to and equivalents ofthe various elements of the embodiments would be understood to those ofordinary skill in the art upon study of this patent document. These andother variations and modifications of the embodiments disclosed hereinmay be made without departing from the scope and spirit of theinvention.

1. A system for measuring the size of a capsular bag of an eye,comprising: a size indicator configured for insertion into a capsularbag of a subject eye and comprising a peripheral portion and a pair ofarms, the peripheral portion configured to engage the capsular bag, thepair of arms each having proximal and distal ends, the arms joined toone another at the proximal ends, the peripheral portion joined to thedistal ends of the arms, the arms forming an angle that depends on asize of the capsular bag, the angle being within a predetermined rangeof angles when the size indicator is placed within the capsular bag; anda sizing gauge, comprising: a body having a front surface; and a firstfeature disposed along or behind the front surface and a second featuredisposed along or behind the front surface; wherein the features areconfigured to correspond to an angle that is within the predeterminedrange.
 2. The system of claim 1, wherein the arms of the size indicatorare configured so that an angle formed by the arms varies in response toa dimension of the capsular bag.
 3. The system of claim 1, wherein thesize of the capsular bag is a diameter of the capsular bag.
 4. Thesystem of claim 1, wherein the size of the capsular bag is a volume ofthe capsular bag.
 5. The system of claim 1, wherein the body is planaror curved.
 6. The system of claim 1, wherein the sizing gauge furthercomprises a grip attached to the body.
 7. The system of claim 1, whereinthe body of the sizing gauge is formed of a material that is opaque. 8.The system of claim 1, wherein the sizing gauge is flexible and isconfigured to be draped over a cornea of the eye.
 9. The system of claim1, wherein sizing gauge is a contact lens.
 10. The system of claim 9,wherein contact lens has no optical power or substantially no opticalpower.
 11. The system of claim 1, further comprising at least onealphanumeric character disposed along or behind the front surface, theat least one alphanumeric character indicating one or more of an anglebetween the pair of arms of the size indicator, a size of the sizeindicator, a size of the capsular bag, a volume of the capsular bag, aresiliency of the capsular bag.
 12. The system of claim 11, wherein theat least one alphanumeric character appears backward when viewed from infront of the front surface.
 13. The system of claim 1, wherein the firstand second features are first and second straight edges, the straightedges forming an angle corresponding an angle within the predeterminedrange of angles.
 14. The system of claim 13, wherein each straight edgeis a line disposed between first and second areas of the body of thesizing gauge.
 15. The system of claim 13, wherein each straight edgedefines an edge of the body of the sizing gauge.
 16. The system of claim13, wherein each straight edge is a different edge of a first notch inthe body of the sizing gauge, the first notch disposed at an edge of thebody.
 17. The system of claim 16, wherein the body of the sizing gaugefurther comprises a second notch having two sides, the second notchdisposed at an edge of the body.
 18. The system of claim 17, wherein theangle between the sides of the first notch is equal to the angle betweenthe sides of the second notch.
 19. The system of claim 16, wherein thesystem comprises a plurality of sizing gauges each having a first notch,the angle between the sides of the first notch of one of the sizinggauges is different than the angle between the sides of the first notchof the remaining sizing gauges of the plurality of sizing gauges. 20.The system of claim 19, wherein the sizing gauges are attached to oneanother to form a set and are individually selectable for comparisonwith the angle between the arms thereof.
 21. The system of claim 13,wherein the body of the sizing gauge further comprises third and fourthstraight edges, the straight edges forming a closed contour when viewedfrom in front of the front surface, the first and second edges forming afirst angle and the third and fourth edges forming a second angle thatis different from the first angle.
 22. The system of claim 1, whereinthe body of the sizing gauge further comprises a vertex mark and thefirst and second features are first and second line segments, the linesegments disposed at different distances from the vertex mark, the linesegments each having first and second end points, the endpoints of thefirst line segment defining a first angle with the vertex mark, theendpoints of the second line segment defining a second angle with thevertex mark that is greater than the first angle.
 23. The system ofclaim 22, wherein the first line segment is parallel to the second linesegment, the line segments being symmetrically disposed about acenterline.
 24. The system of claim 22, wherein the vertex mark is a setof cross-hairs or a circle.
 25. A system for measuring the size of acapsular bag of an eye, comprising: a size indicator configured forinsertion into a capsular bag of a subject eye, the size indicatorcomprising a physical feature having an angle that depends on a size ofthe capsular bag, the angle being within a predetermined range of angleswhen the size indicator is placed within the capsular bag; and a sizinggauge, comprising: a body having an front surface; and a notch disposedat an edge of the body; wherein the notch is configured to correspond toan angle that is within the predetermined range.
 26. A digitalmeasurement system, comprising: an angle indicator comprising anincomplete annulus and a pair of arms joined at an intersectiontherebetween, the arms disposed within the incomplete annulus, the armsoperably coupled to first and second ends of the angle indicator andconfigured so that an angle formed by the arms varies in response to adiameter of a capsular bag of an eye; and an electronic device formeasuring the angle formed by the arms, the electronic devicecomprising: an optical instrument configured to image at least the armsof the angle indicator; a digitizing instrument to convert the image toa digital image; and a measuring device to measure the angle formed bythe arms of the angle indicator from the digital image.
 27. The digitalmeasurement system of claim 26, wherein the optical instrument comprisesa microscope for imaging the arms.
 28. The digital measurement system ofclaim 26, wherein the optical instrument comprises a camera for imagingthe arms.
 29. The digital measurement system of claim 26, wherein theoptical instrument further comprises a calibrated reticle.
 30. Thedigital measurement system of claim 26, wherein the digitizinginstrument comprises a computer for converting the image to a digitalimage.
 31. The digital measurement system of claim 26, wherein themeasuring device comprises software that generates a measured anglevalue for an angle embedded within a digital image.
 32. The digitalmeasurement system of claim 26, further comprising an instrument todisplay the digital image.
 33. The digital measurement system of claim32, wherein the measuring device comprises a protractor.
 34. The digitalmeasurement system of claim 33, wherein the protractor comprises: analignment mark disposed in front of an intersection of the arms of theangle indicator and at least one radial reference edge disposed alongone of the arms; and a plurality of arcuately disposed features locatedat predetermined angular locations from the at least one radialreference edge.
 35. The digital measurement system of claim 33, whereinthe protractor is displayed electronically superimposed over the digitalimage.